The Pittsburgh to St. Louis Main Line was a rail line owned and operated by the Pennsylvania Railroad in the U.S. states of Pennsylvania, Ohio, Indiana, and Illinois. The line ran from Pittsburgh, Pennsylvania west via Steubenville, Ohio, Columbus, Ohio, Dayton, Ohio, Indianapolis, Indiana, Terre Haute, Indiana, and Vandalia, Illinois to East St. Louis, Illinois.[1] In addition to its east end in downtown Pittsburgh, where it met the Main Line and Pittsburgh to Chicago Main Line, junctions included the Columbus to Chicago Main Line at Columbus, the C&X Branch (to Cincinnati) at Xenia, the Columbus to Indianapolis Main Line via Bradford (a freight bypass of Dayton) at New Paris, the Richmond Branch and Fort Wayne Branch at Richmond, the Louisville Branch and I&F Branch at Indianapolis, and the Peoria Branch at Farrington, Illinois.
Large portions of the line have been abandoned; the only major pieces still in use are from Mingo Junction (west of Steubenville) to Columbus, operated by the Columbus and Ohio River Rail Road (Ohio Central Railroad System), and west of Terre Haute, operated by CSX Transportation as part of its St. Louis Line Subdivision. Other existing pieces are from Rosslyn, Pennsylvania to Walkers Mill (Pittsburgh and Ohio Central Railroad), Weirton Junction, West Virginia to Mingo Junction (Norfolk Southern Railway Weirton Secondary), Columbus to London, Ohio (NS Dayton District), Clement, Ohio to Dayton (NS), just east of Richmond, Indiana (NS New Castle District), and from Indianapolis to Ben Davis, Indiana (CSX Crawfordsville Branch Subdivision).[citation needed]